POLLINATION

Pollination, transfer of pollen grains from the stamens, the flower parts that produce them, to the ovule-bearing organs or to the ovules (seed precursors) themselves. In plants such as conifers and cycads, in which the ovules are exposed, the pollen is simply caught in a drop of fluid secreted by the ovule. In flowering plants, however, the ovules are contained within a hollow organ called the pistil, and the pollen is deposited on the pistil’s receptive surface, the stigma. There the pollen germinates and gives rise to a pollen tube, which grows down through the pistil toward one of the ovules in its base. In an act of double fertilization, one of the two sperm cells within the pollen tube fuses with the egg cell of the ovule, making possible the development of an embryo, and the other cell combines with the two subsidiary sexual nuclei of the ovule, which initiates formation of a reserve food tissue, the endosperm. The growing ovule then transforms itself into a seed.

1. POLLINATION
-ADITYA ARYA
B.SC.B.ED. {CBZ}

2. Introduction, types of
pollination
Autogamy & Geitonogamy
CONTENTS !
POLLINATION
Xenogamy, factors facilitating
cross pollination.
SELF POLLINATION
CROSS POLLINATION
1
2
3
Anemophily (Wind),Hydrophily
(Water),Entomophily (Insects),Ornithophily
(Birds),Chiropterophily (Bats),Myrmecophily
(Ants)
4
AGENTS OF POLLINATION

3. ❑The process of transfer and deposition of pollen grains from the another to
the stigmatic surface of the flower is called pollination. It is an essential
event in the sexual reproduction of seed bearing plants. Pollination is a pre-
requisite for ensuring seed set and perpetuation of a species. Pollination is
direct in Gymnosperms and indirect in Angiosperms.
❑There are two main types of pollination
1.Self pollination
2.Cross pollination.
POLLINATION

5. I. Self Pollination
❑It is the process of transfer of pollen grains from the another to the stigma of
either the same flower or another flower borne on the same plant.
❑Accordingly, self pollination is of two types: autogamy and geitonogamy.
(A)Autogamy: (Gk. Auto = self, gamos = marriage):
It is a kind of pollination in which the pollen from the
anthers of a flower are transferred to the stigma of the same
flower.
It occurs by three methods.
(i)Cleistogamy
(ii)Homogamy
(iii)Bud Pollination

6. (i)Cleistogamy: (Gk. Kleisto= closed. Gamos =
marriage):Some plants never open to ensure
complete self-pollination. This condition is called
cleistogamy, eg.Commelinabengalensis, Oxalis, Viola,
etc. The cleistogamous flowers are bisexual small,
inconspicuous, colourlessand do not secrete nectar.
(ii)Homogamy : Anthers and stigma of the bisexual
flowers of some plants mature at the same time. They
are brought close to each other by growth, bending or
folding to ensure self pollination. This condition is
called homogamy, eg., Mirabilis (Four O. clock),
Catharanthus (Vinca), Potato, Sunflower, etc.
(iii)Bud Pollination: Anthers and stigma of the bisexual
flowers of some plants mature before the opening of
the buds to ensure self-pollination, eg., Wheat, Rice,
Pea, etc.
Cleistogamy Homogamy
Bud Pollination

7. (B) Geitonogamy (Gk, geiton = neighbour, gamos = marriage):
It is a kind of pollination in which the pollen grains from the anthers of one flower
are transferred to the stigma of another flower borne on the same plant. It usually
occurs in plants which show monoecious condition (unisexual, male and female
flowers are borne on the same plant).

8. Advantages of self-pollination:
1. Chances of pollination are more.
2. Self-pollination maintains purity of the race and avoids mixing.
3. It need not produce a large number of pollen grains.
4. Flower need not possess devices such as large and showy petals, presence of scent
and nectar, etc. to attract pollinators.
Disadvantages of self-pollination:
1. Progeny continuously gets weaker after
every generation.
2. Less chances of the production of new
species and varieties.

9. II. Cross Pollination :
➢Cross Pollination involves the transfer of pollen grains
from the flower of one plant to the stigamaof the
flower of another plant.
➢It is also called Xenogamy.(Gk. Xenos= Strange,
gamos = marriage) or allogamy (gk, allos= other,
gamos = marriage.

10. The main floral characteristics which facilitate cross pollination are:-
i)Herkogamy:
Flowers are bisexual but the essential organs, the stamens and stigmas, are arranged in
the flower, in such a way that self pollination becomes mechanically impossible.
eg., Hibiscus sps; Gloriosa superba, etc.
Hibiscus : The stigmas project far above the stamens.
Gloriosa superba : The style is reflexed away from the stamens.

11. ii) Dichogamy :
Pollen and stigma of the flower mature at different times
to avoid self pollination.
It is of two types.
a.Protography:Gynoecium matures earlier than
androecium eg.Bajra, Aristolochiaetc.
b.Protandry:Androecium matures and shed pollen
gynoecium eg.maize.
iii) Self-incompatibility:
In some plants, when the mature pollen fall on the receptive stigma of the same flower, it fails
to bring about self pollination. It is called self incompatibility. Under such conditions, the cross
pollination is the only option.
iv) Male sterility :
The pollen grains of some plants are not functional. Such plants set seeds only after cross
pollination.

12. v) Dioecism:
Cross pollination always occurs when the
plants are unisexual and dioecious. i.e. male
and female flowers occur on separate plants.
eg., Papaya, some cucurbits etc.
vi) Heterostyly:
The flowers of some plants have different
lengths of stamens and styles so that self
pollination is not possible
eg.Primula, Linum, etc.

13. AGENTS OF
POLLINATION:
1.Anemophily (Wind)
2.Hydrophily (Water)
3.Entomophily (Insects)
4.Ornithophily (Birds)
5.Chiropterophily (Bats)
6.Myrmecophily (Ants)
Pollination is effected by many
agents like wind, water, insects etc.
On the basis of the agents that
bring pollination, the mode of
pollination is as follows :

14. 1. Anemophily (Wind pollination):
(Gk, anemos= wind, philein= to love)
It is a mode of pollination or transfer of pollengrainsfrom anther to stigma
through the agency of wind. The flowers which are wind pollinated are
called anemophilous.
The anemophilous flowers are characterized by the following adaptations :
(i)Flowers are small colourless, inconspicuous, odourlessand nectarless.
(ii)Calyx and corolla are either reduced or absent. Anthers are usually
versatile.
(iii)When flowers are unisexual, male flowers are more abundant than
female flowers. In bisexual flowers, the stamens are generally
numerous.

15. (iv) Pollen grains are small, light, dry, dusty and sometimes
winged (or saccate) so that they are easily blown away to long
distances (upto1300 km).
(v) Pollen grains of anemophilous flowers are produced in huge
quantities. For example, a single flower of Cannabisproduces,
5,00,000 pollengrains.
(vi) The flowers are well exposed in the air. In certain plants,
they are produced above the foliage before the appearance of
new leaves.
(vii) The stigmas are large, well-exposed, hairy, feathery or
branched to catch the air-borne pollen grains.
(viii)In some plants, (eg., Urtica), the anthers burst suddenly to
throw the pollen grains into the air (gun-powder mechanism)
The common examples of wind pollinated flowers are –
grasses, sugarcance, bamboo, coconut, palm, date palm,
cannabis (bhang), maizeetc.

16. 2. Hydrophily (Water Pollination):
(Gk, Hydro = water, Philein= to love)
Hydrophily occurs only in a few aquatic plants.
Hydrophily is of two types,
-hypohydrophilyand
-epihydrophily.
i) Hypohydrophily:
It is true hydrophily which occurs below the surface of
water.
It occurs in totally submerged plants and their pollen
grains are water borne.
eg., Zostera marina, Ceratophyllum, etc.Hydrophily

17. Ceratophyllumdesnersum:
In Ceratophyllumdesnersum(a submerged
fresh water plant), the male flower bears 30-
45 stamens. The mature anthers break at the
base, rise to the surface of water and dehisce
there. The liberated pollen germinate and sink
in water. While sinking, they come in contact
with stigma of female flowers to effect
pollination.
Zosteramarina:
In Zostera marina, the pollen grains are
elongated (upto2,500 mm), needle like
and without exine. They have the same
specific gravity as that of water, therefore
float below the surface of water. When
they reach the stigma, they oil around it
and germinate.

18. 3. Entomophily (insect Pollination) :
❖The important pollinating insects are bees, butterflies,
moths, wasps, bettlesetc.
❖The insects visit the flowers for nectar, edible pollen
grains or shelter.
❖Bees are the chief visitors of flowers and they obtain
both nectar and pollen from the flowers.
❖They have pollen sacs or pollen baskets for collecting
pollen.
❖The important characteristics of insect pollinated
flowers are as under:
1.The flowers are large or if small they are grouped into
inflorescence.
2.The flowers are usually brightly colouredand have
specific odour.
3.The flowers usually possess nectar or edible pollen.
4.They produce fewer pollen grains.
5.Anthers and stigmas are commonly inserted.
6.Stigmas are usually unbranched and may be flat or
lobed.

19. A detailed study of the inter-relationship between the structure of
flower and insect pollinators clearly indicates that some
angiospermous plants are dependent upon a particular type of insect
for pollination.
Some classic examples are as follows :
Pollination in Salvia:
✓The genus Salvia belongs to family Labiatae (Mint family) in which
the gamopetalous corolla is two-lipped (bilabiate).
✓The lower lip provides platform for the visiting insect and the
upper lip is just like a hood which protects the floral organs.
✓The flowers are protandrous. Each flower has two epipetalous
stamens located in anterio-lateral position.
✓Each stamen has a short filament and an elongated curved
connective. The anther has two parts -one half is sterile and
another half is fertile. Both the parts of anther are separated apart
due to elongation of connective.
✓The elongated connective has two unequal arms. The upper arm is
long and curved. It bears the fertile lobe of anther.

20. ❖The lower arm of connective is short and bears the
sterile lobe of anther.
❖The two sterile lobes jointly form a sterile plate of
tissue which is placed at the mouth of corolla tube and
partly blocks the path of the visiting insect.
❖The upper fertile lobes are sheltered in the upper lip of
corolla.
❖As a bee visits the young flower and moves inward in
search of nectar, its head pushes the sterile plate which
brings down the fertile anther lobes to strike against its
back.
❖The pollen grains are deposited upon the back of the
bee.
❖When the pollen-dusted bee visits older flower (with
protruded bilippedstigma), its back rubs against the
mature stigma bringing about the pollination.
❖Since the bisexual flowers of Salviaare protandrous,
(anthers mature earlier than the gynoecium), cross
pollination occurs only when pollen-dusted bee visits
older flowers with mature gynoecium

21. 4. Ornithophily (Pollination by birds):
▪Ornithophily (Gk. Ornis = bird, philein= to love) is a mode of pollination
performed by birds.
▪The act of pollination is not performed by all the birds except a few. The
most common bird pollinators are Sun bird, Humming bird, Crow, Bulbul,
Parrot, Mynah, etc.
▪The birds visit a large variety of flowers such as Bombax (Red Silk Cotton),
Erythrina (Coral Tree), Callistemon (Bottle Brush), Bignonia, Agave, ete.
Over about 100 species of Australian plants are pollinated by birds.
▪Humming bird pollinates while hovering over the flowers and sucking
nectar.
▪The bird can derive about half of its body weight of nectar in a single day.
The nectar is chiefly made of sugars and provides a sweetdrinkto the bird.

22. The ornithophilousflowers are characterized by
the following adaptations:
i) The flowers are usually large in size. They
have tubular or funnelshapedcorollas.
ii) The flowers are brightly coloured(such as red,
yellow, orange, blue, etc.) which attract the birds
from long distances.
iii) The flowers produce abundant watery nectar

23. 5. Chiropterophily (Bat Pollination):
It is a mode of pollination performed by bats.
•The bats are nocturnal flying mammals which move swiftly and
transport pollen grains to long distances, sometimes over 30
kms.
•The flowers they visit are large, dull-colouredand have a strong
scent. Chiropterophilousflowers produce abundant pollen
grains and secrete more nectar than the ornithophilousflowers.
•Some of the common
chiropterophilousplants are
-Kigeliapinnata (Sausage
Tree), Adansonia (Baobab
Tree), Bauhinia megalandra,
Anthocephalus(Kadam
Tree), etc. Each flower of
Adansonia (Baobab Tree)
has 1500-2000 stamens.

24. 6. Myrmecophily:
▪Sometimes ants take their food or shelter on some
trees such as Mango, Litchi, South American
Acacia and so on.
▪These ants act as body guards of the plants against
any disturbing agent and also helps in pollination.
▪The pollination performed by any type of animal is
called Zoophily.

25. Advantages of cross
pollination :
i) Cross pollination brings about
genetic recombination and
production of new varieties
(variations).
ii) Cross pollination results in
healthy and stronger off springs
due to phenomenon of hybrid
vigour.

26. THANK YOU !
-ADITYA ARYA
B.SC.B.ED. V SEMESTER
ROLL NO. : 04